When flash illumination is used for the capture of an image sometimes the pupils of people in the image appear red. This is caused by light from the flash unit entering the pupil, multiply reflecting off the retina, and finally exiting back through the pupil. Because light is partially absorbed by capillaries in the retina, the pupil appears red in the image. This phenomenon is referred to as “redeye.” The probability of redeye being observed increases the closer the flash unit is to the optical axis of the lens. Therefore, redeye is commonly observed in images captured by a small camera with an integral flash unit.
Commonly assigned U.S. Pat. No. 5,432,863, which is entitled “Automated Detection and Correction of Eye Color Defects Due to Flash Illumination” and which issued Jul. 11, 1995 in the names of Paul J. Benati, Robert T. Gray and Patrick A. Cosgrove, describes a user-interactive method for the detection of objects in an image that have the color characteristic of redeye. This method automatically detects candidate redeye pixels based on shape, coloration, and brightness. Although this presently known method of detecting redeye is satisfactory, it is not without certain drawbacks. For instance, the method disclosed in the '863 patent does not determine whether the candidate pixels are located in a face or are part of a human eye.
Commonly assigned U.S. Pat. No. 6,292,574, which is entitled “Computer Program Product for Redeye Detection” and which issued Sep. 18, 2001 in the names of Jay S. Schildkraut, Robert T. Gray and Jiebo Luo, describes a technique for detecting eye color defects of a subject in an image due to flash illumination based on detecting skin colored regions in a digital image, searching the skin colored regions for groups of pixels with color characteristic of redeye defect, and correcting color of the pixels based on a location of a found redeye defect. A drawback of this technique is its inability to either detect face regions in their entirety or, more specifically, to detect face regions as well separated skin colored regions.
Consequently, a need exists for a technique of detecting redeye that overcomes the above-described drawbacks.